6,073,232
`[11] Patent Number:
`[19]
`United States Patent
`
`Kroeker et al.
`[45] Date of Patent:
`*Jun. 6, 2000
`
`USOO6073232A
`
`[54] METHOD FOR MINIMIZING A
`COMPUTER’S INITIAL PROGRAM LOAD
`TIME AFTER A SYSTEM RESET ()R A
`pOWER_()N USING N0N_V0LATILE
`STORAGE
`
`[75]
`
`Inventors: Richard Mark Kroeker, Morgan Hill;
`Richard Henry Mandel, In San Jose
`both of Calif.
`
`[73] Assignee:
`
`International Business Machines
`Corporation, Armonk, NY.
`
`[*] Notice:
`
`This patent issued on a continued pros-
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`.
`.
`patent
`term prov1s1ons of 35 U.S.C.
`154(a)(2)’
`
`[
`
`l
`
`21
`22
`
`]
`[
`[51]
`[
`l
`[
`l
`
`APPL N0-3 08/806,135
`Filed:
`Feb. 25, 1997
`
`
`Int. Cl.7
`.... .. G06F 9/445
`
` US, Cl, .......... N
`713/1; 713/2; 713/100
`Field of Search ................................... .. 395/651, 652,
`395/653; 713/1, 2, 100
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5/1993 Bealkowski et al.
`5,210,875
`................. .. 395/700
`7/1993 Dayan et al.
`. . . . . . .
`5,230,052
`. . . .. 395/700
`
`5,269,022 12/1993 Shinjo et al.
`......................... .. 395/700
`5,307,497
`4/1994 Feigenbaum et al.
`................ .. 395/700
`5,325,532
`6/1994 Crosswy et al.
`395/700
`
`5,355,498 10/1994 Provinp et al.
`395/700
`
`..
`
`5,404,527
`5,410,699
`
`........................... .. 395/700
`4/1995 Irwin et al.
`4/1995 Bealkowski et al.
`................. .. 395/700
`
`Primary Examiner—Ayaz R. Sheikh
`Assistant Examiner—Tim V0
`
`Attorney, Agent, or Firm—Gray Cary Ware Freidenrich
`
`[57]
`
`ABSTRACT
`
`Amethod for increasing boot speed of a host computer with
`associated hard disk drive generates a prefetch table that
`contains pointers to disk locations and lengths of the records
`of an application program requested by the host computer
`during an initial power-on/reset. During the next power-on/
`reset, before the host computer is ready for data but after the
`disk drive has completed its reset routine, using the prefetch
`table the disk drive accesses the previously requested data
`and copies it onto the cache of the disk drive, from where it
`is transferred to the host computer when the host computer
`requests it. The prefetch table is updated to reflect disk
`location changes for the various records, or to reflect new
`records that were requested by the host computer but not
`found in cache during the previous power-on/reset.
`
`4,663,707
`
`5/1987 Dawson ................................ .. 364/200
`
`33 Claims, 2 Drawing Sheets
`
`30
`
`33
`
`
`
`*M-‘
`
`Y
`
`
`Create and activate
`25
`slive
`
`
`TCBs
`to read data
`Read prefetch
`table from
`
`
`in tbl
`into cache until
`
`disk into RAM
`cache is full.
`
`
`32
`able
`stored since
`reset or pwr-o
`?
`
`33A
`
`N
`Store FGVlSEd
`table 0M0
`o
`Is
`resel‘fVe: kfll'ea
`
`
`
`so
`
`Proceed using
`Receive
`command from existing data access
`host, build T88
`and command
`
`to handle
`processing methods
`
`
`
`
`
`
`
`
`
`
`
`
`
`Stare location
`: 66
`and length of
`Set prefetch
`requested records
`for next
`flag inactive
`
`reset/power—on
`increment
`
`
`flag inactive
`read miss
`Set prefetch
`
`threshold
`flag inactive
`
`
`
`
`
`
`
`
`
`activate a
`TCB
`
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`
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`
`
`
`
`
`
`48
`
`Werement cache
`read miss
`
`count
`50
` Normal read
`cache to host
`processing,
`
`processing,
`disk to cache
`
`
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`

`

`U.S. Patent
`
`Jun. 6, 2000
`
`Sheet 1 of 2
`
`6,073,232
`
`
`
`
`
`Host
`Computer
`
`11,
`
`21
`
`FIG. 2
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`

`US. Patent
`
`Jun. 6,2000
`
`Sheet 2 0f2
`
`6,073,232
`
`30
`
`
`
`Create and activate
`__2_3_.___
`TCBs
`to read data
`Read prefetch
`in tbl
`into cache until
`tame fr°m
`
`(“5k into RAM
`cache is
`full.
`
`
`
`
`
`
` stored since
`reset or pwr-o
`
`7
`
`
`
`
`
`Store revised
`table onto
`reserved area
`of disk
`
`
`
`
`
`
`
`
`se nex
`
`t
`U
`
`table entry
`to build
`and
`activate a
`Tea
`
`55
`
`
`
`56* grafetCh
`flag Inactive
`
`Increment
`
`N
`
`refetch
`flag active
`Y
`
`[,0
`
`Store location
`and length of
`requested records
`for next
`reset/power—on
`
`'
`
`flag inactive
`
`58
`
`
`
`refetch
`lag activ
`
`
`
`54
`
`
`
`FIG. 3
`
`['8
`
`50
`
`1.2
`
`read miss
`threshold
`
`Y
`
`Set prefetch
`flag inactive
`
`41.
`
`46
`Dataf N
`in cache
`
`N
`
`Y
`
`increment cache
`read miss
`count
`
`Normal read
`processing,
`disk to cache
`___¢
`
`
`
`orma rec
`process'"g'
`cache to host
`
`
`
`
`52
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`
`
`
`
`
`Proceed using
`
`existing data access
`and command
`
`
`
`processing methods
`
`Receive
`command from
`
`host, build TCB
`to handle
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`

`6,073,232
`
`1
`METHOD FOR MINIMIZING A
`COMPUTER’S INITIAL PROGRAM LOAD
`TIME AFTER A SYSTEM RESET OR A
`POWER-ON USING NON-VOLATILE
`STORAGE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates generally to peripheral stor-
`age apparatus for computers, and more particularly to short-
`ening the load time of computer programs from a hard disk
`drive to a host computer.
`2. Description of the Related Art
`When a computer undergoes a hardware reset (i.e., a
`power-on or
`reset),
`the computer executes procedures
`embodied in its power-on/reset firmware which prepare for
`loading an operating system into the computer to condition
`it for operation. Typically, execution of such procedures
`begins what is referred to as a “boot”. While the computer
`is executing these power on/reset procedures, peripheral
`devices that are associated with the computer, such as, for
`example, a hard disk drive, also execute their own power-
`on/reset procedures embodied in firmware. When the com-
`puter finishes the above-described firmware-implemented
`portion of the “booting” process, it typically requests data
`from the disk drive as part of initializing user-selected
`software, e.g., a program marketed under one of the trade-
`names DOS, Windows, UNIX, OS/2, AIX, etc.
`It happens that the transfer of the selected program to the
`computer is relatively slow, particularly when the program
`is a modern large operating system. Accordingly, methods
`have been disclosed for increasing the speed with which
`computers “boot”. One example of such a method is dis-
`closed in US. Pat. No. 5,307,497, which teaches that a
`portion of an operating system can be stored in read-only
`memory (ROM) for fast access of the portion during power-
`on or reset. Unfortunately, the portion stored in ROM is
`unchangeable. In other words, the method disclosed in the
`’497 patent does not adapt to changing user preferences
`regarding operating systems, or indeed to updated versions
`of a particular operating system.
`Another example of a previous attempt to shorten the load
`time from a disk drive to its host computer is set forth in US.
`Pat. No. 5,269,022. As disclosed in the ’022 patent, a
`snapshot of computer memory is stored in a backup memory
`that is separate from the disk drive associated with the
`computer,
`for use during the next succeeding boot.
`Unfortunately, the backup memory must be large, because it
`must store the entire computer memory. Also, the method
`disclosed in the ’022 patent requires operating system
`intervention, which, because of security features common to
`many modern operating systems, renders the ’022 invention
`unfeasible.
`
`As recognized by the present invention, however, it is
`possible to provide, without operating system intervention,
`a method for adaptively preparing a disk drive to effect rapid
`application program loading to a host computer. Specifically,
`we have found that during hardware resets the disk drive
`associated with a host computer typically completes its
`booting process before the host computer is ready for
`program transfer, and as recognized by the present
`invention, the disk drive can be configured during this period
`for rapidly communicating a program to the host computer.
`Accordingly, it is an object of the present invention to
`provide a method for rapidly communicating a computer
`program from a disk drive to a host computer.
`
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`2
`Another object of the present invention is to provide a
`method for rapidly communicating a computer program
`from a disk drive to a host computer which adapts to changes
`in user program preference, and to changes in program
`storage location on the disks of the disk drive. Yet another
`object of the present invention is to provide a method for
`rapidly communicating a computer program from a disk
`drive to a host computer which does not require excessively
`large storage space, and which can be undertaken entirely by
`the disk drive itself, transparent to the host computer. Still
`another object of the present
`invention is to provide a
`method for rapidly communicating a computer program
`from a disk drive to a host computer which is easy to use and
`cost-effective.
`
`SUMMARY OF THE INVENTION
`
`The invention is embodied in an article of
`
`is used by a
`manufacture—a machine component—that
`digital processing apparatus and that tangibly embodies a
`program of instructions that are executable by the digital
`processing apparatus to rapidly communicate a computer
`program from a hard disk drive to the drive’s host computer.
`This invention is realized in a critical machine component
`that causes a digital processing apparatus to adaptively store
`a computer program on the cache of the hard disk drive and
`communicate the program to the host computer. Hereinafter,
`the machine component is referred to as a “computer pro-
`gram product”.
`In accordance with the present invention, steps executed
`by the digital processing apparatus include, after an initial
`power-up or reset of the hard disk drive and a host computer
`associated with the drive, receiving an initial read command
`from the host computer for transferring to the host computer
`a plurality of data records of a program stored on the disk.
`Aprefetch table is then generated, with the table represent-
`ing a disk location and length of each data record requested
`by the initial read command. Then, after a subsequent
`power-on or reset of the hard disk drive, and during a second
`power-on or reset of the host computer, the prefetch table is
`accessed to read into the data cache the data records. In
`
`response to a subsequent read command from the host
`computer, it is determined whether records requested by the
`subsequent read command are stored in the data cache. If
`they are, the records are communicated from the cache to the
`host computer; otherwise,
`the records are communicated
`from the disk to the host computer.
`Preferably,
`the accessing and determining steps are
`repeated for each power-on or reset of the host computer.
`The steps executed by the digital processing apparatus
`further include either incrementing a read counter toward a
`predetermined value, fixed in the algorithm or programmed
`by the user or adaptively determined based on system
`environmental conditions, or decrementing a counter
`towards zero using the same process described for the
`incrementing condition when it is determined during the
`determining step that records requested by the subsequent
`read command are not stored in the data cache. As used
`
`generally herein, then, “incrementing” a counter refers both
`to incrementing and decrementing a counter. Additionally,
`the steps further include updating the data prefetch table,
`communicating the records from the disk to the host com-
`puter when the read counter exceeds a predetermined
`threshold, and setting a prefetch flag to inactive when the
`read counter exceeds the predetermined threshold.
`In the presently preferred embodiment, the invention also
`includes setting the prefetch flag to inactive when a prede-
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`6,073,232
`
`3
`termined number of write commands from the host com-
`
`puter to the hard disk drive have been received. Moreover,
`the invention can include, after the communicating step and
`when the prefetch flag is inactive, determining whether the
`hard disk drive is idle and if so, storing the prefetch table on
`the disk. The computer program product is disclosed in
`combination with the hard disk drive, and in combination
`with the host computer.
`In another aspect, a computer program product is dis-
`closed for use with a host computer that is coupled to a hard
`disk drive. The hard disk drive includes at least one storage
`disk having a program stored thereon and a data cache, and
`the computer program product includes a data storage device
`which includes a computer usable medium having computer
`readable program means. As disclosed in detail below, these
`code means are for enhanced loading of the program from
`the hard disk drive to the host computer during power-on or
`reset of the host computer. In accordance with the present
`invention, code means receive a command from the host
`computer during a power-up or reset of the host computer.
`When the command is a read command, code means gen-
`erate a prefetch table representative of at least
`the disk
`location of the records requested by the read command for
`transfer of the records from the disk to the cache for a
`
`subsequent power-on or reset of the host computer.
`Moreover, code means are provided for determining whether
`the records have been stored in the cache in response to a
`previous power-on or reset of the host computer, and the
`records are communicated to the host computer in response.
`In still another aspect, a computer hard disk drive includes
`at least one data storage disk and a data storage cache.
`Furthermore, the hard disk drive includes means for record-
`ing onto the cache, immediately after a hardware reset of the
`hard disk drive, data on the disk that has been requested by
`a host computer during a first hardware reset of the host
`computer. Additionally, the disk drive includes means for
`communicating the data from the cache to the host computer
`during a second hardware reset of the host computer.
`The details of the present invention, both as to its structure
`and operation, can best be understood in reference to the
`accompanying drawings, in which like reference numerals
`refer to like parts, and in which:
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a partially schematic view of a disk drive with
`associated host computer, with portions broken away for
`clarity;
`FIG. 2 is an illustration of memory such as read-only
`memory (ROM),
`random access memory (RAM),
`electrically-erasable programmable read only memory
`(EEPROM), or dynamic random access memory (DRAM)
`containing microcode,
`that embodies the invention as a
`program storage product; and
`FIG. 3 is a flow chart showing the method steps of the
`present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Referring initially to FIG. 1, a system is shown, generally
`designated 10, for promoting rapid communication of a
`computer program from a hard disk drive 12 to a host
`computer 14 that is in data communication with the disk
`drive 12 in accordance with principles well-known in the art.
`In one intended embodiment, the host computer 14 may be
`a personal computer (PC) or laptop computer made by IBM
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`4
`Corp. of Armonk, NY. Or, the host computer 14 may be a
`UniX computer, or OS/2 server, or Windows NT server, or
`IBM RS/6000 250 workstation. Indeed, the host computer
`14 can be an embedded controller that is part of a music
`synthesizer, or part of an industrial instrument. And, the hard
`disk drive 12 can be any hard disk drive suitable for
`computer applications, provided that the hard disk drive 12
`includes at least one, and typically a plurality of, data storage
`disks 16 and an on-board, solid state,
`random access
`memory (RAM) data cache 18.
`As shown in FIG. 1, the hard disk drive 12 also includes
`an onboard controller 20. In accordance with principles
`well-known in the art, the onboard controller 20 is a digital
`processor which, among other things, controls read heads 22
`in the disk drive 12 for effecting data transfer to and from the
`disks 16.
`
`Additionally, as intended by the present invention the
`onboard controller 20 includes an adaptive cache module 24.
`Per the present invention, the adaptive cache module 24 is
`executed by the onboard controller 20 as a series of
`computer-executable instructions. These instructions are
`embodied as microcode in a memory, e.g., read-only
`memory (ROM) of the onboard controller 20. Such a ROM
`is indicated by reference numeral 21 in FIG. 2. The ROM 21
`contains microinstructions that embody means and program
`steps that perform according to the invention. When in the
`ROM 21, the microinstructions become part of the ROM 21,
`and therefore, part of the hardware of the disk drive 12.
`Those skilled in the art will appreciate that the hard disk
`drive is merely illustrative of a particular tangible environ-
`ment that is useful for understanding the concepts of our
`invention. Broadly,
`the hard disk drive 12 represents a
`peripheral storage apparatus. The hard disks 16 of the hard
`disk drive 12 represent data storage elements that are found
`in the general peripheral storage apparatus. The invention,
`therefore, applies to such a peripheral storage apparatus and
`a data storage element, and should not be limited to a hard
`disk drive.
`FIG. 3 illustrates the structure of such microinstructions
`
`as embodied in a computer program. Those skilled in the art
`will appreciate that FIG. 3 illustrates the structures of
`computer program code elements that function according to
`this invention. Manifestly, the invention may be practiced in
`its essential embodiment by a machine component, embod-
`ied by the ROM 21, that renders the computer program code
`elements in a form that instructs a digital processing appa-
`ratus (e.g., the onboard controller 20) to perform a sequence
`of function steps corresponding to those shown in the
`Figures. The machine component is shown in FIGS. 1 and
`2 as a combination of program code elements A—C in
`computer readable form that are embodied in a computer-
`usable data medium (the ROM 21) of the onboard controller
`20. Such media can also be found in other semiconductor
`
`devices, on magnetic tape, on optical disks, on floppy
`diskettes, on a DASD array, on a conventional hard disk
`drive, in logic circuits, in other data storage devices, or even
`in a node of a network. In an illustrative embodiment of the
`
`invention, the computer-executable instructions would be in
`object code form, compiled or assembled from a C++ lan-
`guage program and stored, by conventional means, in the
`ROM 21. Or, the code used can be an interpretative code
`such as Forth, Smalltalk, or Java and its derivatives.
`Referring in detail to FIG. 3, the method of the present
`invention can be seen. It is to be understood that in the
`
`presently preferred embodiment, the method begins imme-
`diately after the hard disk drive 12 has completed its
`power-on/reset (i.e., hardware reset) routine.
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`6,073,232
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`5
`Commencing at start state 26, the process moves to block
`28, wherein a prefetch table is read from a reserved area of
`the disks 16 into the RAM cache 18. As discussed further
`
`the prefetch table contains a listing of the disk
`below,
`locations and lengths of data records that were requested by
`the host computer 14 in the immediately previous power-
`on/reset. Additionally, a copy of a prefetch flag, if enabled
`by the user, is created and set active at block 28. In other
`words, the prefetch flag is preferably defined to be active by
`the user of the hard disk drive 12 to enable the adaptive
`caching of the present
`invention. If desired,
`the default
`setting of the prefetch flag can be set to active. The original
`prefetch flag resides on the disk and is settable by the user
`(setting the features for IDE, and setting the mode pages for
`SCSI), and the copy of the prefetch flag is what is used for
`all steps discussed below, except where indicated otherwise.
`Next, at block 30, task control blocks (TCBs) are created
`and initiated in accordance with well-known principles to
`read the data represented by the prefetch table from the disks
`16 into the RAM cache 18. The method then enters an idle
`
`state 32 to await a command from the host computer 14.
`During the idle state 32, the process can move to decision
`diamond 33 to determine whether the prefetch table has been
`stored since the latest power on or reset. Also, it is deter-
`mined whether the original prefetch flag is active and
`whether the copy of the flag is inactive. If the original flag
`is active, the copy is not, and the table has not been stored
`since the latest power on/reset, (and, if desired, a disk drive
`idle time has been exceeded), then the process moves to
`block 33A to store the table onto the area of the disk reserved
`for the table. From block 33A or from decision diamond 33
`
`if any one of the above-noted conditions have not been met,
`the logic moves back to the idle state 32.
`At block 34, a command is received from the host
`computer 14, and a task control block (TCB) is accordingly
`built to support the command. From block 34, the process
`moves to decision diamond 36 to determine whether the
`
`command received from the host computer 14 is a read
`command.
`
`If the command is a read command, indicating that the
`host computer 14, pursuant to its initialization, is requesting
`data records that are part of a computer program such as
`DOS or Windows, the process moves to decision diamond
`38 wherein it is determined whether the prefetch flag is
`active. If it is, the process continues to block 40, wherein the
`disk location and length of the record requested by the read
`command is recorded in the prefetch table for the next
`power-on/reset. Thus, at block 40 the prefetch table is
`updated to reflect a newly requested record, or to reflect a
`new disk location of a previously-requested record. Then, it
`is determined at decision diamond 42 whether a read miss
`
`counter exceeds a predetermined read miss threshold. If so,
`the prefetch flag is set to inactive at block 44.
`The skilled artisan will recognize that
`the read miss
`threshold represents a predetermined number of cache
`misses. Per the present invention, the read miss threshold
`can be a programmed integer, or it can be an adaptively
`determined integer. For example, the read miss threshold can
`be calculated as a predetermined fraction of total cache
`“hits”. Or, the read miss threshold can be calculated as the
`number of misses beyond which a predetermined percentage
`of the records requested by the host computer 14 cannot be
`retrieved from the cache 18.
`
`From block 44, or from decision diamonds 38 or 42 when
`the decisions there are negative,
`the process moves to
`decision diamond 46 to determine whether the requested
`
`6
`data exists in cache. If not, a cache read miss counter
`(initialized at zero) is incremented by one at block 48, and
`the requested record is transferred from the disks 16 to the
`host computer 14 using normal processing at block 50. (As
`the skilled artisan will recognize, a counter can instead by
`initialized to a predetermined value and then decremented
`instead of incremented, in which case the test at decision
`diamond 42 would be changed to “is the read miss counter
`greater than zero?”). From block 50, or from decision
`diamond 46 if it was determined that the requested data
`exists in cache, the process moves to block 52 to transfer the
`record from cache 18 to the host computer 14.
`
`the method
`After the read processing just described,
`proceeds to decision diamond 54 to determine whether the
`copy of the prefetch flag is active. If it is active, the logic,
`at block 56, uses the next entry in the prefetch table to build
`a task control block (TCB) to fetch data into the same
`segment of the cache 18 that the just-transferred record had
`occupied prior to being communicated to the host computer
`14. In accordance with the present invention, the TCB in
`block 50 is activated as though a command otherwise was
`received across the device/file interface. In other words,
`when the host computer 14 is a PC, the TCB in block 50 is
`activated as though a command otherwise was received
`across the SCSI (or IDE)—disk drive interface. In this way,
`the relatively small amount of cache storage space can be
`optimally used during the adaptive caching process until all
`records designated in the prefetch table have been loaded
`into cache and then transferred to the host computer 14.
`Also, if desired the process updates the data in the cache 18
`of the disk drive 12 in response to the step undertaken at
`block 56. Stated differently, at block 56 the next entry in the
`prefetch table is copied from the disks 16 to the data cache
`18. The control then loops back to idle state 32.
`
`Thus, the above discussion is directed to the condition
`wherein a read command is received. Recall that this deci-
`
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`
`sion is made at decision diamond 36. In contrast to the steps
`executed as described above, when it
`is determined at
`decision diamond 36 that the command received at block 34
`
`45
`
`50
`
`55
`
`60
`
`65
`
`is not a read command, the logic moves to decision diamond
`58 to determine whether the command is a write command.
`
`If the command is not a write command, the process moves
`to block 60 to proceed using existing data access and
`command processing methods, and then the process contin-
`ues back to the idle state 32.
`
`If, however, the command received at block 34 is a write
`command, the process moves to decision diamond 62 to
`determine whether the copy of the prefetch flag is active. If
`not, the logic loops back to block 60, but otherwise the logic
`moves to decision diamond 64 to determine whether a write
`
`miss counter exceeds a predetermined write miss threshold.
`If it does, the prefetch flag copy is set to inactive at block 66.
`Otherwise, the write miss counter is incremented at block
`68. From blocks 66 and 68 the process loops back to block
`60. If desired, while the disk drive 12 is idle, the data on the
`disks 16 that was requested by the host computer 14 is
`reordered on the disks 16 for accessing the data into cache
`during the next power-on/reset with a minimum of latency
`and seek times.
`
`The method just described and illustrated in FIG. 3 may
`be realized in a computer program in, for example, the C++
`language, when commonly known programming techniques
`are employed with reference to the pseudo code represen-
`tation in Table I.
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`6,073,232
`
`TABLE I
`
`A high-level pseudo-code representation of a computer program embodying the invention
`for a hard disk drive sequence after power-on through the first X number of READ commands from
`a host computer.
`1) disk drive diagnostics successfully complete
`2) all drive cache segments are filled with data that was requested from the previous
`power-on
`the power-on prefetch table is read from the reserved area on the disk into
`SRAM
`a series of tasks are initiated, by creating task control blocks (TCB) and
`starting them much like they would normally be started upon command
`receipt, to read the data the power-on prefetch table points to into data buffer
`RAM.
`3) drive goes into its idle loop
`4) command is received from host
`5) a TCB is built to handle command
`6)
`is the command a read?
`Y) is the prefetch flag active?
`Y) store the location and length of the requested record for the
`subsequent power-on or reset cycle.
`cache read miss threshold exceeded?
`Y) set prefetch flag inactive
`data in cache?
`N) increment cache read miss count
`normal read processing, set up hardware and start transfer, disk to
`cache
`prefetch flag active?
`Y) when transfer complete, use next entry in prefetch tabte to build TCB
`to fetch data into same segment as last transfer. TCB is activated as
`if a command was received across the interface.
`N) is the command a write?
`Y) Prefetch flag active?
`Y) write threshold count exceeded?
`Y) set prefetch flag inactive
`N) increment write threshld count
`proceed using existing data access and command processing methods
`7) whenever command is received from host, go to
`8) during idle time the revised table is stored onto the reserve area of the disk (only
`done once per power on/reset session).
`
`Note <a>: The file side code (software that works very close to the disk side of the hardware, as
`opposed to the IDE/SCST or host side of the hardware) operates quasi-independently from host side
`code (it is linked together through TCBs and other global variables). The hardware can support con-
`current host and file side operations.
`
`40
`
`While the particular METHOD FOR MINIMIZING A
`COMPUTER’S INITIAL PROGRAM LOAD TIME
`AFTER A SYSTEM RESET OR A POWER-ON USING
`NON-VOLATILE STORAGE as herein shown and
`described in detail is fully capable of attaining the above-
`described objects of the invention, it is to be understood that
`it
`is the presently preferred embodiment of the present 45
`invention and is thus representative of the subject matter
`which is broadly contemplated by the present invention, that
`the scope of the present invention fully encompasses other
`embodiments which may become obvious to those skilled in
`the art, and that
`the scope of the present
`invention is 50
`accordingly to be limited by nothing other than the appended
`claims.
`We claim;
`1. Acomputer program product for use with a peripheral
`storage apparatus including at least one data storage element 55
`and a data cache, comprising:
`a computer program storage medium readable by a digital
`processing apparatus; and
`a program means on the program storage medium and
`including instructions executable by the digital pro-
`cessing apparatus for causing the digital processing
`apparatus to copy data stored on the data storage
`element to the data cache by:
`after an initial power-up or reset of the peripheral
`storage apparatus and a host computer associated
`with the peripheral storage apparatus, receiving a
`read command from the host computer for transfer-
`
`60
`
`65
`
`ring to the host computer a data record of a program
`stored on the data storage element;
`in response to receiving, generating and storing in the
`peripheral storage apparatus a prefetch table repre-
`sentative of a storage location and length of the data
`record requested by the initial read command;
`after a subsequeht Power'Oh .Or reset 0f the Peripheral
`Storage apparatus; ahd dhrlhg a SeeOhd Power'oh or
`reset 0f the hOSt ComPhtera aeeeSSlhg by the Perlph'
`eral Storage .aPParathS the Prefeteh table to read the
`. data record 1ht0 the data caChe; and
`1h reSPOhse t0 Shhseqheht read commands from the hOSt
`comPhtera determlhlhg Whether records reqheSted by
`the subsequent read commands are stored in the data
`cache, and if so, communicating the records from the
`data cache to the hOSt COIhPhtera ahd OtherWise
`commuhlcatlhg the records from the data Storage
`element to the host computer.
`2. The computer program product of claim 1, wherein
`accessing and determining are repeated for each power-on or
`reset of the host computer,
`the program means further
`causing the digital processing apparatus to:
`increment a read counter when it
`is determined that
`records requested by the subsequent read command are
`not stored in the data cache.
`3. The computer program product of claim 1, wherein the
`program means further causes the digital processing appa-
`ratus to update the data prefetch table.
`4. The computer program product of claim 1, in combi-
`nation with the storage apparatus.
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`6,073,232
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`9
`5. The computer program product of claim 2, wherein the
`program means further causes the digital processing appa-
`ratus to:
`
`communicate the records from the data storage element to
`the host computer when the read counter exceeds a
`predetermined threshold; and
`set a prefetch flag to inactive when the read counter
`exceeds the predetermined threshold.
`6. The combination of claim 4, in further combination
`with the host computer.
`7. The computer program product of claim 4, wherein the
`storage apparatus is a disk drive.
`8. The computer program product of claim 5, wherein the
`program means further causes the digital processing appa-
`ratus to set the prefetch flag to inactive when a predeter-
`mined number of write commands from the host computer
`to the peripheral storage apparatus have been received.
`9. The computer program product of claim 5, wherein the
`program means further causes the digital processing appa-
`ratus to:
`
`after communicating, when the prefetch flag is inactive,
`determine whether the peripheral storage apparatus is
`idle and if so, store the prefetch table on the data
`storage element.
`10. The computer program product of claim 7, wherein
`the data storage element is a disk.
`11. A computer program product for use with a host
`computer coupled to a peripheral storage apparatus includ-
`ing at least one data storage element having a program stored
`thereon and a data cache, comprising:
`a data storage device for use within a periph